Remove more obsolete MC code.

This should be the last of the code for the edge labels and vector
 interpolation.
Fix compilation without USE_BAND_PARTITIONS.
fix pathological case of building for CC=c++

* enum <-> int conversion has to be explicit
* extern linkage for const arrays must be explicit
* {m,c,re}alloc returned pointers must be cast
* Use const char * when appropriate
* Return value of dct.c's main (i.e. the test) was being set to a garbage value.
tools: fix building for CC=c++
Only use extern when necessary
Add tool for submitting jobs to AreWeCompressedYet
tools: Don't leak fds in submit_awcy.py
block_size: fix documentation